1. Field of the Invention
The present invention relates to telecommunication systems and, in particular, to a method and system for transmitting short messages between mobile communication systems which are based on different mobile communication standards.
2. Description of Related Art
There are currently in the world a number of digital mobile communication systems based on different mobile communication standards and protocols. Mobile communication networks, such as GSM (Global System for Mobile communications) networks, have become very popular in a large part of the world. In the United States, however, which is of course considered an important country when considering mobile communication systems, several other and incompatible mobile communication standards are now in use. More particularly, there are at present at least two digital mobile systems in use in the United States: DAMPS (Digital Advanced Mobile Phone System), which is based on the S-54 standard and which is compatible with the analog AMPS (Advanced Mobile Phone System) implementation, as well as CDMA (Code Division Multiple Access) which is based on the IS-95 standard. American mobile communication systems are ultimately based on the ANSI-41 trunk network standard. In addition, Japan has a mobile communication system that is based on its own, different standard JDC (Japan Digital Cellular).
Since the introduction of digital mobile networks, the services provided by and through such networks have included the short message service (SMS), which has rapidly become very popular throughout the world. The short message service is in actuality a radio paging system in which alphanumeric messages may be transmitted to the mobile subscriber, who can then read these messages on the subscriber's mobile station display whenever the subscriber wishes to do so. The transmission of short messages in the various different systems and protocols in use throughout the world is very similar, but these various implementations are nevertheless not wholly compatible. This has caused a particularly disadvantageous situation that results in significant difficulties and impediments when one wishes to send a short message between mobile communication systems that are based on different standards.
One especially significant problem that has arisen is the lack, under those circumstances, of a roaming feature for short messages as a connective factor between different mobile communication systems.
The term roaming is generally used to denote the co-operation of system operators through which the user of a mobile station is able to establish a connection in a wider area than just that user's own operator can offer. To enable roaming between different systems the system operators involved must agree with each other on the administration of inter-system roaming and adapt their systems to the technical and operating requirements necessary to effect the desired communication and co-operation between their respective systems.
Such roaming functionality has been available for phone calls, as between the GSM system operators of Europe, but other problems have arisen as a result of poor compatibility between different mobile communication systems. Cooperation between system operators of different mobile communication systems based on different standards has not heretofore enabled the use of roaming between such different systems for short messaging services.